4.20-stable review patch. If anyone has any objections, please let me know.
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[ Upstream commit 66f71da9dd38af17dc17209cdde7987d4679a699 ]
Since a2468cc9bfdf ("swap: choose swap device according to numa node"), avail_lists field of swap_info_struct is changed to an array with MAX_NUMNODES elements. This made swap_info_struct size increased to 40KiB and needs an order-4 page to hold it.
This is not optimal in that: 1 Most systems have way less than MAX_NUMNODES(1024) nodes so it is a waste of memory; 2 It could cause swapon failure if the swap device is swapped on after system has been running for a while, due to no order-4 page is available as pointed out by Vasily Averin.
Solve the above two issues by using nr_node_ids(which is the actual possible node number the running system has) for avail_lists instead of MAX_NUMNODES.
nr_node_ids is unknown at compile time so can't be directly used when declaring this array. What I did here is to declare avail_lists as zero element array and allocate space for it when allocating space for swap_info_struct. The reason why keep using array but not pointer is plist_for_each_entry needs the field to be part of the struct, so pointer will not work.
This patch is on top of Vasily Averin's fix commit. I think the use of kvzalloc for swap_info_struct is still needed in case nr_node_ids is really big on some systems.
Link: http://lkml.kernel.org/r/20181115083847.GA11129@intel.com Signed-off-by: Aaron Lu aaron.lu@intel.com Reviewed-by: Andrew Morton akpm@linux-foundation.org Acked-by: Michal Hocko mhocko@suse.com Cc: Vasily Averin vvs@virtuozzo.com Cc: Huang Ying ying.huang@intel.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- include/linux/swap.h | 11 ++++++++++- mm/swapfile.c | 3 ++- 2 files changed, 12 insertions(+), 2 deletions(-)
diff --git a/include/linux/swap.h b/include/linux/swap.h index d8a07a4f171d..3d3630b3f63d 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -233,7 +233,6 @@ struct swap_info_struct { unsigned long flags; /* SWP_USED etc: see above */ signed short prio; /* swap priority of this type */ struct plist_node list; /* entry in swap_active_head */ - struct plist_node avail_lists[MAX_NUMNODES];/* entry in swap_avail_heads */ signed char type; /* strange name for an index */ unsigned int max; /* extent of the swap_map */ unsigned char *swap_map; /* vmalloc'ed array of usage counts */ @@ -274,6 +273,16 @@ struct swap_info_struct { */ struct work_struct discard_work; /* discard worker */ struct swap_cluster_list discard_clusters; /* discard clusters list */ + struct plist_node avail_lists[0]; /* + * entries in swap_avail_heads, one + * entry per node. + * Must be last as the number of the + * array is nr_node_ids, which is not + * a fixed value so have to allocate + * dynamically. + * And it has to be an array so that + * plist_for_each_* can work. + */ };
#ifdef CONFIG_64BIT diff --git a/mm/swapfile.c b/mm/swapfile.c index 20d3c0f47a5f..dbac1d49469d 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -2813,8 +2813,9 @@ static struct swap_info_struct *alloc_swap_info(void) struct swap_info_struct *p; unsigned int type; int i; + int size = sizeof(*p) + nr_node_ids * sizeof(struct plist_node);
- p = kvzalloc(sizeof(*p), GFP_KERNEL); + p = kvzalloc(size, GFP_KERNEL); if (!p) return ERR_PTR(-ENOMEM);